Meaningful collaborative interactions in asynchronous online mathematics teacher professional development (PD) may provide teachers with valuable opportunities to learn. We studied collaborative interactions in online teacher PD activities that involved embedded videos, prompts, discussions, and multiple online tools. Analysis of teacher responses highlighted different levels of collaborative interactions across activities and the importance of providing teachers with learning opportunities that prompt them to take into account others' perspectives in an online environment. We share implications for research on and design of mathematics teacher PD and activities related to these interactions.